Page 37 - Ilmu Tanah

24 The Chemistry and Fertility of Soils under Tropical Weeds

contained as part of the soil solid structures of primary and secondary (precipitate)
minerals and organic matters.
Plant roots may quickly absorb free ions. Dissolved complexes, chelated, and
adsorbed ions may quickly satisfy the depletion in the concentration of free ions in
soil water following Eq. 2.2, Eq. 2.4, and Eq. 2.6, respectively.

a-
0
m+
M + A  M a A m ……. Eq. 2.2

with

0
[ ]
K = ……. Eq. 2.3
[ + ][ − ]

m+
a-
0
where M is a nutrient element cation, A is the complexing anion, M a A m is the
related complex ion, and K is the reaction constant.

l-
0
m+
M + L  M l L m ……. Eq. 2.4

with

0
[ ]
K = ……. Eq. 2.5
[ + ][ − ]

m+
0
l-
where M is a nutrient element cation, L is the ligand, M l L m is the related
chelate, and K is the reaction constant.
m+
n+
X-M + N  X-N + M ....... Eq. 2.6
with

+
[ ]
K = + ……. Eq. 2.7
[ ]

where X is the soil adsorption sites, M and N are nutrient element cations, and X-M
and X-N are adsorbed nutrient elements. All of these reactions may buffer the
concentrations of free ions in the soil water to satisfy their absorption by plant
roots. The equilibrium concentration is controlled by the respective reaction
constant. The relationship between these reactions is depicted in Fig. 2.2. Some
examples of free and complex ions and organic chelates in soils are listed in Table
2.1.
Abdul Kadir Salam and Nanik Sriyani – 2019